Liquid crystal display device having electrostatic discharge protection

ABSTRACT

A liquid crystal display device includes a plurality of gate lines and a plurality of data lines substantially perpendicular to the gate lines, first and second shorting bars formed respectively in a gate driving IC mounting region and a data driving IC mounting region. A plurality of switching devices are formed between the first shorting bar and respective pad of the gate lines and between the second shorting bar and respective pad of the data lines.

This is a continuation of application Ser. No. 08/969,367 filed on Nov.28, 1997 now U.S. Pat. No. 6,025,891. This application claims thebenefit of Korean Patent Application No. 59212/1996 filed Nov. 29, 1996,which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) device,and more particularly, to a liquid crystal display device for mounting achip on glass (COG) to facilitate an array check.

2. Discussion of the Related Art

Generally, many methods for mounting a driving integrated circuit (IC)exist which provide a signal for driving an LCD device. Such methodsinclude the wire bonding (WB) type, the tape automated bonding (TAB)type, and the COG-type.

The WB type method connects a panel electrode with a driving IC using Auwire. The TAB-type method mounts a package on a panel, in which adriving IC is connected to a film carrier. The COG-type method mounts abump formed on a bare chip for a panel having an inner lead pad and anouter lead pad.

During the process steps of forming an LCD device, electrostaticdischarge occurs in an internal TFT-LCD array, which destroys internaldevices, such as a thin film transistor. For this reason, a shorting barhas been used to prevent the internal devices from being destroyed bythe electrostatic discharge and facilitate array checking after formingan array region of a TFT-LCD.

In general, a first shorting bar is connected to respective gate linesand a second shorting bar is connected with respective data lines. Apower source is applied to the shorting bar bar connected to the gatelines to check for open lines at end of the respective gate linesopposite to the shorting bar when performing a continuity check of thearray. A similar technique is also applied to the data lines.

The shorting bar is not actually used in driving the TFT-LCD. Theshorting bar is removed once it has performed the functions ofprotecting the TFT-LCD from electrostatic discharge and checking thearray for continuity. In other words, if the array continuity check issuccessful after forming the TFT-LCD array, a top plate of the TFT-LCDand a bottom plate thereof are bonded to each other. The shorting bar isremoved by a scribe and a grinding process.

Meanwhile, the respective gate lines and the respective data lines havedifferent configurations from each other depending on the methodutilized for mounting the driving IC, which causes difficulty in formingthe shorting bar. In the TAB-type method for mounting a driving IC, thecarrier film is connected to both sides of a bare chip so that a spaceon the TFT-LCD panel is ensured. In this case, a shorting bar is formedat one side of each of a gate line pad and a data line pad, which servesas driving IC mounting regions. In the COG-type mounting method, theinner lead and the outer lead should be formed within the driving ICmounting region of the TFT-LCD panel, because it is difficult to ensurea space on the TFT-LCD panel, thereby causing difficulty in forming ashorting bar in the driving IC mounting region. To overcome theabove-mentioned shortcoming, a method for mounting a shorting bar usingthe COG-type mounting method has been recently developed.

A conventional method for mounting a shorting bar in an LCD deviceemploying the COG-type mounting method will be described with referenceto FIG. 1, which is a schematic layout illustrating a conventional LCDdevice employing a COG-type mounting method.

As illustrated in FIG. 1, a plurality of gate lines 1 are formed on asubstrate in one direction at a predetermined interval and a pluralityof data lines 2 are formed in a direction perpendicular to the gatelines 1 at a predetermined interval. Gate line pads 3 and data line pads4 are respectively formed at one end of each of the respective gatelines 1 and data lines 2. A plurality of gate input pads 7 are formed ata predetermined interval opposite the gate line pads 3. A plurality ofdata input pads 8 are formed at a predetermined interval opposite thedata line pads 4.

A gate driving IC mounting region 9 includes the gate line pads 3 andthe gate input pads 7. A data driving IC mounting region 10 includes thedata line pads 4 and the data input pads 8. In these driving IC mountingregions 9 and 10, first and second shorting bars 5 and 6 are formed,respectively. The first shorting bar 5 is formed between the respectivegate line pads 3 and the respective gate input pads 7. The respectivegate line pads 3 are connected to the first shorting bar 5. The secondshorting bar 6 is formed between the respective data line pads 4 and therespective data input pads 8. The respective data line pads 4 areconnected to the second shorting bar 6.

In FIG. 1, reference numeral 11, which is not described, represents alaser cutting line.

A TFT-LCD having thin film transistors and pixel electrodes is formedand the array continuity check is performed. A top plate of the TFT-LCDand a bottom plate thereof are then adhered to each other and theshorting bars 5 and 6 are severed from the gate line pads 3 and the dataline pads 4 using a laser cutting equipment.

However, the conventional LCD device employing the COG-type mountingmethod has a disadvantage in that the cost of production increases dueto the shorting bar being severed from the respective gate or data linepads using expensive laser cutting equipment.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a liquid crystaldisplay device that substantially obviates one or more of the problemsdue to limitations and disadvantages of the related art.

An object of the present invention is to provide a liquid crystaldisplay device for facilitating array continuity checking.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims thereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a liquidcrystal display device according to the present invention includes aplurality of gate lines and a plurality of data lines perpendicular tothe gate lines, first and second shorting bars formed respectively in agate driving IC mounting region and a data driving IC mounting region,and a plurality of switching devices formed between the first shortingbar and respective pads of each of the gate lines and between the secondshorting bar and respective pad of each of the data lines.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 is a schematic layout illustrating a conventional LCD deviceemploying a COG-type mounting method;

FIG. 2 is a schematic layout illustrating a LCD device employing aCOG-type mounting method;

FIGS. 3(a) and 3(b) are schematic layouts illustrating switching devicesfor the respective gate and data line regions according to the firstembodiment of the present invention;

FIG. 4 is a schematic layout illustrating a shorting bar region and aTFT-LCD region according to the first embodiment of the presentinvention;

FIG. 5 is a sectional view along line I--I of FIG. 4 of the shorting barregion, for the gate lines, and the TFT-LCD region of the presentinvention;

FIGS. 6(a)-6(d) illustrates the manufacturing steps of the shorting barregion, for the gate lines, and the TFT-LCD represented in FIGS. 4 and 5of the present invention;

FIGS. 7(a) and 7(b) are schematic layouts illustrating switching devicesfor the respective gate and data lines according to the secondembodiment of the present invention;

FIG. 8(a) is a schematic layout illustrating a shorting bar region and aTFT-LCD region according to the second embodiment of the presentinvention;

FIG. 8(b) is a sectional view along line II--II of FIG. 8(a) of theshorting bar region, for the gate lines, and the TFT-LCD region of thepresent invention;

FIG. 9(a) is a schematic layout illustrating a shorting bar region and aTFT-LCD region according to the third embodiment of the presentinvention; and

FIG. 9(b) is a sectional view along line II--II of FIG. 9(a) of theshorting bar region, for the gate lines, and the TFT-LCD region of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

As illustrated in FIG. 2, a plurality of gate lines 1 are formed on asubstrate in one direction at a predetermined interval and a pluralityof data lines 2 are formed perpendicularly to the gate lines 1 at apredetermined interval.

Gate line pads 3 and data line pads 4 are formed at one of the ends ofthe gate lines 1 and the data lines 2, respectively. A plurality of gateinput pads 7 are formed at predetermined intervals to oppose the gateline pads 3. A plurality of data input pads 8 are formed atpredetermined intervals to oppose the data line pads 4.

A gate driving IC mounting region 9 includes the gate line pads 3 andthe gate input pads 7. A data driving IC mounting region 10 includes thedata line pads 4 and the data input pads 8. In driving IC mountingregions 9 and 10, first and second shorting bars 5 and 6 arerespectively formed.

The first shorting bar 5 and each of the respective gate line pads 3 areconnected with each other by switching devices 12. The second shortingbar 6 and each of the respective data line pads 4 are connected witheach other by switching devices 12.

In other words, the first shorting bar 5 is formed between each of therespective gate line pads 3 and the respective gate input pads 7. Eachof the respective gate line pads 3 is then connected to the firstshorting bar 5 through the switching device 12. The second shorting bar6 is formed between each of the respective data line pads 4 and the datainput pads 8. The respective data line pad 4 is connected to the secondshorting bar 6 through the switching device 12, wherein the respectiveswitching device 12 is turned on/off by an external signal.

The switching device of the aforementioned LCD device employing aCOG-type mounting method according to the first embodiment of thepresent invention will now be described in detail with reference to FIG.3-FIG. 6. In the first embodiment of the present invention, atransistor, as shown in FIGS. 3(a) and 3(b), is used as the switchingdevice, which is formed in the same manner as the process steps offorming a TFT-LCD cell.

In the gate driving IC mounting region 9, a metal is deposited on aglass substrate and selectively removed to form gate lines 1 and a gateline pads 3 of a TFT-LCD, and at the same time a gate electrode 21, of aswitching device 12, is formed which connects the shorting bar 5 withthe gate line pad 3. A gate insulating film 40 is then formed on theentire surface of the substrate.

As shown in FIGS. 4, 5, and 6(a)-6(d), a semiconductor layer is nextformed on the gate insulating film 40 and selectively removed to form anisland shaped first active layer 22a, above the gate electrode 1a (FIG.5) in the respective thin film transistor region of a TFT-LCD arrayregion. A second active layer is concurrently formed on the gateinsulating layer 40 above gate electrode 21 and the island shaped activeregion 22 is formed in the switching device region. A metal is thendeposited on the entire surface of the substrate and selectively removedto form data lines 2 and data pads 4 (FIG. 3b), in the TFT-LCD arrayregion and a source electrode 23 a drain electrode 24, of the switchingdevice 12, and a first shorting bar 5 are concurrently formed in theswitching device region. Furthermore, the source electrode 23 and thefirst shorting bar 5 are preferably integrally and concurrently formedand the drain electrode 24 is formed to be in contact with the gate linepads 3.

The data driving IC mounting region 10 has a similar construction as thegate driving IC mounting region 9. That is the shorting bar 6 and thedata electrode 21a of the switching device 12 are formed together withthe data lines 2 and the data line pads 4 of the TFT-LCD array region.The source electrode 23 and the drain electrode 24, of the switchingdevice 12, and the gate lines 3 are formed concurrently and the sourceelectrode 23 is in contact with the second shorting bar 6. The drainelectrode 24 and the data line pads 4 are preferably integrally formed.

The switching device of the aforementioned LCD device employing aCOG-type mounting method, according to the second embodiment of thepresent invention, will now be described in detail with reference toFIGS. 8(a) and 8(b). In the second embodiment of the present invention,a diode, as shown in FIGS. 7(a) and 7(b), is used as the switchingdevice 12, which is formed in a similar manner as the process steps forforming a TFT-LCD cell.

In the gate driving IC mounting region 9, a metal is deposited on aglass substrate and selectively removed to form gate lines 1 and gateline pads 3 of a TFT-LCD. A first shorting bar 5 and a gate electrode 21of the switching device 12 are concurrently formed. The gate electrode21 of the switching device 12 and the first shorting bar 5 arepreferably integrally formed.

A gate insulating film 40 is then formed on the entire surface of thesubstrate. A semiconductor layer is next formed on the gate insulatingfilm and selectively removed to form a first active layer 22a in therespective thin film transistor region of TFT-LCD array region.Concurrently, a second active layer 22 is formed on the gate insulatingfilm 40, above the gate electrode 21, in a region for forming theswitching device 12. A metal is then deposited on the entire surface ofthe substrate and selectively removed to form a gate line 1 and a gatepad 3 in the TFT-LCD array region. A source electrode 23 of theswitching device 12 and a drain electrode 24 thereof are formedconcurrently in the switching device region. The source electrode 23 isformed in contact with the first shorting bar 5 and the drain electrode24 is in contact with each of the respective gate pads 3.

With respect to the data driving IC mounting region 10, it is formed insubstantially the same manner with substantially the same structure asthe gate driving IC mounting region 9. The gate electrode 21 of theswitching device 12 and the second shorting bar 6 are formed togetherwith the data line 2 and the data line pad 4 of the TFT-LCD arrayregion. The source electrode 23 and the drain electrode 24 of theswitching device 12 are formed concurrently. The second shorting bar 6and the data electrode 21a are then integrally formed at this time. Thesource electrode 23 is in contact with the second shorting bar 6. Thedrain electrode 24 and the data line 2 are integrally formed.

The switching device of the aforementioned LCD device employing aCOG-type mounting method, according to the third embodiment of thepresent invention, will now be described in detail with reference toFIGS. 9(a) and 9(b). In the third embodiment of the present invention, adiode, as shown in FIGS. 7(a) and 7(b), is used as the switching device12, which is formed in the same manner as the process steps for forminga TFT-LCD cell.

In the gate driving IC mounting region 9, a metal is deposited on aglass substrate and selectively removed to form gate lines 1 and gateline pads 3 of a TFT-LCD. The source electrode 23 of the switchingdevice 12 and the first shorting bar 5 are preferably integrally formed.

A gate insulating film 40 is then formed on the entire surface of thesubstrate. A semiconductor layer is next formed on the gate insulatingfilm and selectively removed to form a first active layer 22a in therespective thin film transistor region of TFT-LCD array region.Concurrently, a second active layer 22 is formed on the gate insulatingfilm 40, above the gate electrode 21, in a region for forming theswitching device 12. A metal is then deposited on the entire surface ofthe substrate and selectively removed to form a gate line 1 and a gatepad 3 in the TFT-LCD array region. A source electrode 23 of theswitching device 12 and a drain electrode 24 thereof are formedconcurrently in the switching device region. The source electrode 23 isformed in contact with the first shorting bar 5 and the drain electrode24 is in contact with each of the respective gate pads 3. The shortingbar 6 and the source electrode 23 are preferably integrally formed.

With respect to the data driving IC mounting region 10, it is formed insubstantially the same manner with substantially the same structure asthe gate driving IC mounting region 9. The gate electrode 21 of theswitching device 12 and the second shorting bar 6 are formed togetherwith the data line 2 and the data line pad 4 of the TFT-LCD arrayregion. The source electrode 23 and the drain electrode 24 of theswitching device 12 are formed concurrently. The source electrode 23 isin contact with the second shorting bar 6 and preferably formedintegrally. The drain electrode 24 and the data line 2 are integrallyformed.

An array check of the aforementioned LCD device employing a COG-typemounting method of the present invention is performed as follows. In theembodiment where the transistor is used as the switching device, in thesame manner as in the first embodiment of the present invention, a highvoltage greater than a threshold voltage of the transistor is applied tothe gate electrode 21 of the switching device 12 for the arraycontinuity check. Once the switching device is turned on, the arraycheck is performed in the conventional manner.

After the LCD device is completed, the power source is disconnected fromthe shorting bar so that the transistor cannot be operated. Since theshorting bar and the input pads are connected to the active layer whichhas a high resistance, it is not necessary to additionally remove theshorting bar.

In the case where a diode is used as the switching device, in the samemanner as the second embodiment and third embodiments of the presentinvention, the power source is applied to the respective lines inaccordance with the forward characteristic of the diode after applyingthe power source to the shorting bar. The array continuity check is thenperformed in the same manner as in the conventional method. After theLCD device is completed, the power source is disconnected-from theshorting bar.

The COG-type LCD device according to the present invention has thefollowing advantages. The shorting bar is mounted in the driving ICmounting region and the switching device is mounted between the shortingbar and each of the respective pads. The shorting bar is connected to orcut off from the pad using the switching device as occasion demands soas to facilitate an array continuity check. Since a laser cuttingprocess is not required, the overall process is simplified and expensivelaser cutting equipment is not required.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the liquid crystal displaydevice according to the present invention without departing from thespirit or scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of the inventionprovided they come within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. A liquid crystal display device comprising:aplurality of first lines, wherein each first line is one of a gate lineand a data line; a plurality of second lines substantially perpendicularto the first lines, wherein each second line is the other one of thegate line and the data line; a first driving IC mounting region; aplurality of first line pads on the first driving IC mounting region andcoupled to the first lines; a plurality of first input pads on the firstdriving IC mounting region; a first shorting bar between the first inputpads and the first line pads; and a plurality of first switching devicescoupled between the first shorting bar and the first line pads, whereinthe first shorting bar remains in the liquid crystal display deviceafter a completion of a manufacture of the liquid crystal displaydevice.
 2. The liquid crystal display device of claim 1, furthercomprising:a second driving IC mounting region; a plurality of secondline pads on the second IC mounting region and coupled to the secondlines; a plurality of second input pads on the second driving ICmounting region; a second shorting bar between the second input pads andthe second line pads; and a plurality of second switching devicescoupled between the second shorting bar and the second line pads.
 3. Theliquid crystal display device of claim 1, wherein the first switchingdevices include transistors.
 4. The liquid crystal display device ofclaim 3, wherein at least two of the transistors share a common gateelectrode.
 5. The liquid crystal display device of claim 4, whereinsources of the transistors are coupled to the first shorting bar, andthe drains of the transistors are each coupled to a respective one ofthe first line pads.
 6. The liquid crystal display device of claim 1,wherein the first switching devices include diodes.
 7. The liquidcrystal display device of claim 6, wherein the diodes have a transistorstructure including a source electrode and a gate electrode commonlyconnected to the first shorting bar.
 8. The liquid crystal displaydevice of claim 1, wherein the first lines are gate lines, and thesecond lines are data lines.
 9. A liquid crystal display devicecomprising:a plurality of first lines, wherein each first line is one ofa gate line and a data line; a plurality of second lines substantiallyperpendicular to the first lines, wherein each second line is the otherone of the gate line and the data line; a plurality of first line padscoupled to the first lines; a first shorting bar; and a plurality offirst transistors, each coupled between the first shorting bar and arespective one of the first line pads, wherein at least two of the firsttransistors share a first common gate electrode.
 10. The liquid crystaldisplay device of claim 9, wherein sources of the first transistors arecoupled to the first shorting bar, and the drains of the firsttransistors are coupled to a respective one of the first line pads. 11.The liquid crystal display device of claim 9, further comprising:aplurality of second line pads coupled to the second lines; a secondshorting bar; and a plurality of second transistors, each coupledbetween the second shorting bar and a respective one of the second linepads.
 12. The liquid crystal display device of claim 11, wherein atleast two of the second transistors share a second common gateelectrode.
 13. The liquid crystal display device of claim 12, whereinsources of the second transistors are coupled to the second shortingbar, and the drains of the second transistors are coupled to arespective one of the second line pads.
 14. The liquid crystal displaydevice of claim 9, wherein the first lines are gate lines, and thesecond lines are data lines.